Technical Field
The present disclosure relates generally to the field of melting glass-forming materials using a melter, and methods of use thereof to produce molten glass, and more specifically to methods and systems for making well-fined molten glass, and glass products therefrom, using one or more melters, for example submerged combustion melters.
Background Art
A submerged combustion melter (SCM) may be employed to melt glass batch and/or waste glass materials to produce molten glass by passing oxygen, oxygen-enriched mixtures, or air along with a liquid, gaseous and/or particulate fuel (some of which may be in the glass-forming materials), directly into a molten pool of glass, usually through burners submerged in a glass melt pool. The introduction of high flow rates of products of combustion of the oxidant and fuel into the molten glass, and the expansion of the gases cause rapid melting of the glass batch and much turbulence and foaming.
Molten glass produced from an SCM is generally a homogeneous mixture of molten glass and fine bubbles. The bubbles may occupy up to 40 percent or more of the volume of molten glass produced with fine bubbles distributed throughout the molten mass of glass. For glass forming operations requiring well-fined (essentially void free) molten glass, a very large number of bubbles must be removed from the molten glass. The typical procedure for removing the bubbles is to allow a long enough residence time in one or more apparatus downstream of the SCM for the bubbles to rise to the surface and burst. Clearing bubbles from the molten glass is referred to as “fining” within the glass industry. Experience with SCMs has shown that the fining process can be very slow due to the bubbles collecting at the molten glass surface forming a layer of stable foam thereon. Formation of this foam layer in downstream fining chambers retards the fining mechanism as well as the heat penetration into the glass from fining chamber combustion burners firing above the glass.
Use of skimmers within the foam layer has been used to hold back some of the upper foam layers allowing the lower, less foamy layers to pass through to flow channels downstream of the SCM. These efforts have been somewhat effective but may require multiple skimmers to obtain a foam free glass layer and surface. In addition, the skimmers are prone to failure during operation making them no longer useful in holding back the upper foam layers and can fall into and partially block downstream flow channels, impeding some or all of the glass flow to downstream apparatus such as forming stations. It is also conventional to use a submerged throat positioned between a melter and a downstream channel, or between first and second sections of a melter; however, these throats are used primarily to serve as a demarcation between an upstream melting region and a downstream fining region. Other methods use a flat-bottom refining or conditioning channel downstream of the melter. In some cases the flat-bottom refining or conditioning channel is movable into and out of fluid communication with the effluent of the melter therefrom, therefore decoupling the melter and downstream glass forming apparatus. However, such arrangements require long refiners and long residence times to sufficiently remove entrained bubbles.
At least for these reasons, it would be an advance in the glass manufacturing art to solve one or more problems of bubble removal and/or surface foam buildup, preferably both problems, while increasing operational flexibility during processing molten glass having a high concentration of gas bubbles such as produced by submerged combustion melting, thereby allowing formation of well-fined molten glass, and glass products using the well-fined molten glass.